CHEVY TWO STRANGE NOISES

Just wondering if any of you know possible causes of these two noises I hear:

1) There is a noise which sounds like it is coming from the front passenger's side, either under the hood or near the tire. At first it seemed like the noise was related to acceleration. It was a faint noise (a woosh sound) when accelerating. I thought something was rubbing, but last night I noticed the sound while idling with the transmission in park. So I'm thinking it must be either a moving part under the hood, or could it be a vacuum leak? It didn't last long enough for me to get out and isolate the sound. Any thoughts?

2) When in 4WD I noticed that when I turn sharp left (on hard packed rock/gravel) something to do with the drive of the front tires makes a loud thud with every couple of inches I travel and sends a vibration through the vehicle.

Any thoughts as to what these sounds might be? Thanks in advance for any input you can provide.